An adhesive applied to an optical device such as a display device may be specifically used for interlayer adhesion of a multilayered structure, or may be used to hermetically seal parts which require moisture resistance. As the adhesive, a photo-curable adhesive may be used, and the photo-curable adhesive may be prepared by making a composition in which a photo-curable oligomer, a photo-crosslinkable monomer, a photoinitiator, and other additives are mixed, and curing the composition by means of photo-energy such as ultraviolet rays. As a component included in the composition for an adhesive, a benzophenone-based compound may be used, and specifically, a benzophenone-based compound having a functional group capable of reacting by light irradiation may be used. Specifically, the functional group capable of reacting by light irradiation may be a (meth)acrylate group, and a benzophenone having a (meth)acrylate group may be prepared by introducing the (meth)acrylate group into a chemical structure of benzophenone.
As a method for preparing a benzophenone having the (meth)acrylate group, Korean Patent Application Laid-Open No. 10-2011-0094309 describes a method for reacting hydroxybenzophenones and (meth)acrylic anhydride in the presence of catalytic amounts of acid, and EP 0346788 describes a method for reacting isocyanatoalkyl (meth) acrylates and hydroxybenzophenones by using a basic catalyst.
These existing preparation methods include a process of reacting the aforementioned components under an acid catalyst or a base catalyst, and may cause a problem in that the acid catalyst or the base catalyst and by-products produced during the process of neutralizing the acid catalyst or the base catalyst cause corrosion. Therefore, when the methods are applied to an optical device, and the like, durability may deteriorate, and as a result, there is a need for a method for preventing such a concern.